Many watersheds throughout the country are approaching or already exceeding their allowable pollutant loading capacities referred to as total maximum daily loads (“TMDLs”). As a result, it is becoming increasingly important for watershed management to provide an economical way for ensuring that the TMDLs are not exceeded. Watershed management is important for watersheds not only because TMDLs for many watersheds are currently defined, but also because many existing TMDLs are expected to be revised and TMDLs for many other watersheds are expected to be promulgated in the near future. The changes to the TMDLs will likely have a significant impact on the treatment costs for both point and non-point sources of pollutants. The United States Environmental Protection Agency published a Water Quality Trading Policy on Jan. 13, 2003, which is hereby incorporated by reference, stating that a market-based approach to water quality trading can provide flexibility and achieve water quality and environmental benefits greater than would otherwise be achieved under more traditional regulatory approaches. A market-based, water quality trading approach can be used by utilities, industries, county governments, and so on to achieve economically sound development and meet the EPA's water quality goals.
Any such water quality trading should factor in the high degree of uncertainty that results from various watershed processes such as rainfall runoff, soil erosion, sediment delivery, pollutant generation, and so on. It is desirable to have a tool to assist in analyzing water quality trading potentials that factor in this uncertainty.